It does mean Black in the context, but it doesn't refer to race. It refers to the chimney sweeper that is on the front side of the package there. Chimney sweepers dress in black and are always covered with soot, hence the negro reference. I believe the original candy was pitch black, though they've added additional flavors since. You might ask, why use a chimney sweeper to decorate the packaging of your candy product? Well, who WOULDN'T want their candy associated with soot? Yummy.

i knew about the good luck connotation of chimney sweeps, cause that's true here in germany, too. shortly after we moved into this house, the doorbell rang and - lo & behold - a chimney sweep was standing there. i didn't want to be bold and touch him (which is what you're supposed to do here), but i did take it as a very positive omen.